EP0728810A2 - Aqueous composition for the protection of tires against ozone and migrating additives - Google Patents

Abstract

An aq. compsn. contains (a) a (co)polymer with Tg below 0 degrees C, based on a (meth)acrylic or vinyl ester; and (b) a compsn. contg. (i) a hydrophilic SiO2 and (ii) a (co)polymer with Tg above 25 degrees C, based on an (meth)acrylic or vinyl ester.

Description

The invention relates to the surface condition of tires and in particular their protection against the consequences of migration to the surface of the various antioxidant and antiozonant agents which they contain.

It is known that certain polymers, and in particular vulcanized rubber compositions based on diene polymers comprising ethylenic double bonds in their main chain are very sensitive to the action of ozone.

When an article produced with such a diene elastomer composition is subjected to the action of a stress in the presence of ozone, the harmful action of ozone is manifested by the appearance of surface cracks oriented perpendicular to the direction of the constraint. If this stress persists or whenever it occurs, cracks develop and can cause the complete rupture of the article.

To limit this degradation, elastomeric compositions commonly incorporate anti-zone chemical compounds as well as waxes. Antiozone chemical compounds slow down the formation and propagation of cracks under static and dynamic stress conditions. Waxes provide additional static protection by forming a protective coating on the surface.

These means of combating the degradation due to ozone have proven their effectiveness. Unfortunately, the most effective antiozone compounds are also characterized by a very strong ability to migrate through their polymeric substrate and to stain and color the adjacent surfaces. For example, yellowish or brown spots appear on the surface of the sidewalls of tires. This phenomenon is called "coloring". Surface migration of waxes also changes the appearance outside of the surfaces of the elastomeric compositions, making it dull and gray. This phenomenon is called the "efflorescence" of waxes.

These migrations are particularly damaging in the case of "whitewall" tires, but they can also seriously penalize the aesthetic appearance of "blackwall" tires which see their outer surfaces change from a shiny to dull and greyish appearance.

To preserve the aesthetic appearance of the white sidewalls of tires until they are put into service, protective coatings are usually used. These coatings are applied to the sidewalls after the manufacture of the tires. They are mainly made on the basis of polyvinyl alcohol ("PVA") softened by plasticizers and include "barrier" agents, for example mica particles, to slow the migration to the surface of these anti-zone chemical agents and these waxes. Patent US5149591 describes one of these protective coatings. However, these coatings are visible, thick, have limited mechanical strength and must be removed before the tires are actually put into service. The present invention proposes to solve these problems.

The mechanical behavior of non-crosslinked polymers varies as a function of temperature, from a vitreous zone at low temperatures, where the behavior is vitreous, that is to say rigid and brittle, to a zone of fluid flow at high temperatures. Between these two areas is an area called "rubber plateau" where the behavior is rubbery, that is to say close to that of an elastomer, as soon as the molecular weight of the polymer is sufficient for there to be entanglements (see: "Viscoelastic Properties of Polymers", John D. Ferry, 3rd. ed, John Wiley & Sons, 1980, especially chapters 10, 12 and 13).

The “glass transition temperature” of a polymer (“Tg”) is called the temperature where the mechanical behavior of the polymer changes from this vitreous, rigid and brittle behavior, to this rubbery behavior. This glass transition temperature is an essential characteristic of polymers.

Glass transition temperatures are usually determined by differential enthalpy analysis (see Introduction to Thermal Analysis: techniques and applications - Michael E. Brown - Ed. Chapman and Hall - New York 1988). This technique, better known by the initials DSC (Differential Scanning Calorimetry), consists in determining the variations in specific heat of a sample whose temperature is raised. It makes it possible to highlight transitions or reactions which are accompanied by energy release (exothermic) or energy absorption (endothermic). The glass transition is an endothermic transition.

The subject of the invention is an aqueous composition intended to form an anti-migration and anti-zone protective coating on the external surface of a tire, this coating being such that it does not have to be removed when these tires are actually put into service.

• (a) un polymère appelé constituant I, ledit constituant I étant un homopolymère ou un copolymère à base d'au moins un monomère choisi dans le groupe des esters acryliques, méthacryliques et vinyliques, et ayant une température de transition vitreuse inférieure à 0°C; et
• (b) un constituant II choisi dans le groupe constitué par une silice hydrophile et un homopolymère ou un copolymère à base d'au moins un monomère choisi dans le groupe des monomères acryliques, méthacryliques et vinyliques, ledit homopolymère ou copolymère ayant une température de transition vitreuse supérieure à 25°C.

The aqueous composition according to the invention comprises an aqueous emulsion of at least:

• (a) a polymer called component I, said component I being a homopolymer or a copolymer based on at least one monomer chosen from the group of acrylic, methacrylic and vinyl esters, and having a glass transition temperature of less than 0 ° C. ; and
• (b) a constituent II chosen from the group consisting of a hydrophilic silica and a homopolymer or a copolymer based on at least one monomer chosen from the group of acrylic, methacrylic and vinyl monomers, said homopolymer or copolymer having a glass transition temperature above 25 ° C.

The constituent I chosen can, in particular, be a copolymer of butyl acrylate and styrene with a content by weight of styrene of the order of 20%. The glass transition temperature of such a polymer is - 21 ° C.

Such an aqueous composition makes it possible to form a continuous, flexible and adherent coating on the surface of the tire even in the absence of plasticizer. This coating opposes migrations to the surface of all the anti-zone agents present in the rubber mixtures of the tire without the need to add a barrier agent such as mica and it opposes by its presence the degradations due with ozone. The rubber behavior of the coating obtained enables it to resist all the deformations undergone between the manufacture and marketing of tires, and even later.

aurait un revêtement formé avec comme seul constituant principal le constituant I précédent. Ce caractère collant est préjudiciable à la résistance mécanique du revêtement et le rend sensible aux poussières et salissures car il s'encrasse facilement.The presence of component II reduces the stickiness that

would have a coating formed with the preceding constituent I as the main constituent only. This stickiness is detrimental to the mechanical resistance of the coating and makes it sensitive to dust and dirt because it easily clogs.

action sur le caractère collant, la silice renforce les propriétés mécaniques du revêtement formé.Component II can be a hydrophilic silica with a content by weight of between 5 and 25 parts per 100 parts of dry polymer. Preferably, the silica content is between 10 and 15 parts. In addition to the

action on the stickiness, silica strengthens the mechanical properties of the coating formed.

According to an alternative embodiment, component II is a homopolymer or a copolymer based on at least one monomer chosen from the group of acrylic, methacrylic and vinyl monomers, said component II having a glass transition temperature above 25 ° C.

Such a constituent II can, in particular, be a copolymer or a mixture of homopolymers of ethyl acrylate and methyl methacrylate with a proportion by weight of ethyl acrylate of the order of 55%, or of polyacetate vinyl. In these two cases, the proportion by weight of component II is between 35 and 55 parts by weight per 100 parts of dry polymer. Below 35 parts, the tackiness of the coating formed is often still marked and above 55 parts, the coating obtained, stiffened, hardly follows the deformations undergone by the tires.

Component II can also be polyvinyl alcohol in the proportion of 10 to 50 parts by weight per 100 parts of dry polymer.

According to another example, component II is poly (N-vinyl-2-pyrrolidone) in the proportion of 10 to 40 parts by weight per 100 parts of dry polymer.

In the latter two cases, when the content of constituent II exceeds the maximum values indicated, the coating formed becomes too rigid as well as too sensitive to the action of water.

Component II can also be a copolymer of polyvinyl alcohol and poly (N-vinyl-2-pyrrolidone).

According to another variant of the invention, the aqueous composition can comprise, in addition to constituent I and of constituent II composed either of a copolymer or of a mixture of homopolymers of ethyl acrylate and methacrylate of methyl with a proportion by weight of ethyl acrylate of the order of 55%, or polyvinyl acetate, a constituent III consisting of a water-soluble vinyl homopolymer or copolymer chosen from the group of polyvinyl alcohols, poly (N-vinyl-2-pyrrolidone) and vinyl alcohol / N-vinyl-2-pyrrolidone copolymers.

The addition of this component III makes it possible to improve the wetting of the composition on the rubber surface and the mechanical resistance of the coating formed after drying.

au moins trois constituants I, II et III a pour 100 parties de polymère sec :

• (a) de 50 à 75 parties de constituant I;
• (b) de 15 à 28 parties de constituant II;
• (c) de 7 à 25 parties de constituant III.

Advantageously, this variant of the composition according to the invention d

at least three constituents I, II and III has per 100 parts of dry polymer:

• (a) from 50 to 75 parts of constituent I;
• (b) from 15 to 28 parts of constituent II;
• (c) from 7 to 25 parts of constituent III.

The different variants of aqueous composition according to the invention can all advantageously comprise a hydrophilic silica in the proportion of 5 to 30 parts by weight per 100 parts of dry polymer. This silica has a thixotropic effect which facilitates the application of the aqueous composition to the rubber surface. On the other hand, the level of silica present in the composition makes it possible to change the appearance of the coating obtained after drying from a shiny appearance (rate from 0 to 10 parts approximately) to a matt appearance (rate of the order of 20 to 30 parts) through all the possible nuances.

invention peut aussi inclure des agents tensioactifs pour favoriser le mouillage sur la surface caoutchoutique.Advantageously, the aqueous composition according to l

The invention may also include surfactants to promote wetting on the rubber surface.

avantage de produire des revêtements transparents qui ne masquent pas les différents marquages apposés sur les flancs des pneumatiques lors de leurs fabrications et de leurs tests, ces revêtements sont ainsi utilisables pour la protection de flancs blancs.The previous compositions have l

advantage of producing transparent coatings which do not mask the various markings affixed on the sidewalls of tires during their manufacture and their tests, these coatings can thus be used for the protection of white sidewalls.

To give a particular aesthetic character to the protected rubber surface, the aqueous composition according to the invention can also comprise pigments. In particular, these pigments can be carbon black to avoid bleaching of the coating obtained after prolonged contact with water or in areas of significant deformation.

In known manner, this aqueous composition can also include anti-foaming agents to facilitate application with a gun.

• l'eau ;
• la silice, si nécessaire ;
• le noir de carbone ou tout pigment, si nécessaire ;
• l'agent tensioactif actif ;
• l'agent anti-mousse, si nécessaire ;
• l'alcool polyvinylique ou la polyvinyle pyrrolidone selon le cas et si nécessaire ;
• le constituant I ou les constituants I et II selon le cas.

To prepare an aqueous composition according to the invention, the following are successively introduced into a container:

• the water ;
• silica, if necessary;
• carbon black or any pigment, if necessary;
• the active surfactant;
• anti-foaming agent, if necessary;
• polyvinyl alcohol or polyvinyl pyrrolidone as the case may be and if necessary;
• constituent I or constituents I and II as the case may be.

The components of the aqueous composition are introduced cold. The mixture is stirred with known means until a complete dispersion of the products of the aqueous composition is obtained, then the emulsion obtained is filtered through a 150 μm nylon fabric to remove any small lumps of poorly dispersed material.

• on applique sur ladite surface caoutchoutique une couche mince d'une composition aqueuse précédente ;
• on laisse sécher ladite couche jusqu'à la formation d'un revêtement de protection.

The subject of the invention is also a method of anti-migration and anti-zone protection of a tire surface in which:

• a thin layer of a preceding aqueous composition is applied to said rubber surface;
• said layer is allowed to dry until the formation of a protective coating.

The application can be done by all known means, and in particular by brush, roller or by spraying with a gun.

To have good mechanical strength of the coating formed after the drying of the aqueous composition, it is essential to apply the composition in one or more successive thin layers. Good results are obtained with dry coatings with a total thickness of between 1 and 30 μm. Preferably, the coatings have a thickness of 3 to 15 μm.

Preferably, the application is made to the external surface of new tires to guarantee their non-coloring by the migration of anti-zone chemical agents to the surface at least during all the transport, storage and test operations until they are put into use. service.

In addition, as the mechanical resistance of the coating formed is high, this coating can withstand all the preceding operations and remain in place after the tires have been put into service and thus ensure for several thousand kilometers and / or several months by its presence maintaining a quality aesthetic appearance as well as effective protection against ozone.

Even if the coating can be sensitive to abrasions, impacts that the sidewalls of tires in service can undergo, it has the other advantage of being removed by wear in the form of a fine crumb without peeling in a manner almost undetectable at 'eye.

Of course, the protective coating cannot be effective on all the parts of the tire in permanent contact with the ground, such as the tread, because its wear is then very rapid. It is however very advantageous to deposit it on the entire surface because it covers and protects the tread before its use and then continues its action on all the other parts which are not in contact with the ground, such as the sides and the troughs of the sculptures.

The invention is illustrated by means of the following examples which should not constitute a limitation of its scope.

• "coloration/efflorescence" : test de l'aptitude du revêtement à s'opposer aux migrations en surface de tous les agents antiozone ;
• "manutention" : test de la résistance mécanique du revêtement lors d'opérations de manutention et de montage sur jante des pneumatiques (ce test impose des déformations de surface des flancs supérieures à 40 % d'extension) ;
• "tenue en dynamique" : test de la résistance mécanique du revêtement sous sollicitation dynamique, 12000 kilomètres sur une rouleuse avec une flèche imposée de 35 % à 60 kilomètres par heure, ce test impose une déformation dynamique en surface des flancs de l'ordre de 15 % d'extension ;
• "frottement " : test de la résistance mécanique du revêtement lors d'opérations de frottement des pneumatiques les uns contre les autres ;
• "râpage trottoir" : frottement du flanc revêtu d'un pneumatique contre un trottoir pendant quelques mètres, test du mode d'élimination du revêtement due à un frottement mécanique, usure en poudrette ou décollement ;
• "eau" : test de la résistance du revêtement lors d'une immersion prolongée dans l'eau, c'est une simulation du stockage longue durée d'un véhicule sur un parking dans une flaque d'eau ;
• "chaleur" : test en étuve à 50°C de la résistance du revêtement pendant au moins six mois ;
• "tenue mécanique après vieillissement" : exposition aux intempéries de pneumatiques revêtus suivie d'un test de résistance mécanique du revêtement ;
• "vieillissement/aspect" : observation visuelle de l'aspect esthétique du revêtement après dépôt et en cours de vieillissement ;
• "lavage" : test de la résistance du revêtement au lavage par frottement avec une solution aqueuse additionnée de savon ;
• "dépôt" : appréciation de la facilité d'application de la composition sur une surface caoutchoutique.

In the examples, the properties of the compositions are evaluated as follows:

• "coloration / efflorescence": test of the ability of the coating to oppose surface migrations of all the antiozone agents;
• "handling": test of the mechanical resistance of the coating during handling and mounting operations on the rim of tires (this test requires surface deformation of the sidewalls greater than 40% of extension);
• "dynamic resistance": test of the mechanical resistance of the coating under dynamic stress, 12000 kilometers on a rolling machine with an imposed deflection of 35% at 60 kilometers per hour, this test imposes a dynamic deformation on the surface of the flanks of the order of 15% extension;
• "friction": test of the mechanical resistance of the coating during operations of friction of the tires against each other;
• "sidewalk grating": rubbing of the sidewall covered with a tire against a sidewalk for a few meters, test of the method of removing the coating due to mechanical friction, wear in crumb or peeling;
• "water": test of the resistance of the coating during prolonged immersion in water, it is a simulation of the long-term storage of a vehicle in a parking lot in a puddle;
• "heat": test in an oven at 50 ° C of the resistance of the coating for at least six months;
• "mechanical strength after aging": exposure to weathering of coated tires followed by a test of the mechanical resistance of the coating;
• "aging / appearance": visual observation of the aesthetic appearance of the coating after deposition and during aging;
• "washing": test of the resistance of the coating to washing by rubbing with an aqueous solution containing soap;
• "deposition": appreciation of the ease of application of the composition on a rubber surface.

acrylate d'éthyle et de méthacrylate de méthyle (Tg :+34°C***); ⁽⁵⁾ émulsion aqueuse à 54% de polyacétate de vinyle (Tg : 28 à 31°C*); ⁽⁶⁾ silice amorphe hydrophile : Aérosil 200 (Degussa); ⁽⁷⁾ agent tensioactif non ionique : Octyl Phényl Polyoxyde d'éthylène (Cinnopal OP9 de Henkel); ⁽⁸⁾ agent anti-mousse : BYK 070 (BYK).
* Référence : Encyclopedia of Chemical Technology, 3ème édition, vol. 23.
** Référence : mesures Rhône-Poulenc.
*** Référence : mesures internes.

Table 1 presents the formulations of the coatings tested, and Table 2 the results obtained. The formulations are presented using 100 parts of dry polymer as a base. TABLE 1 Composition AT B VS D E F G H I J K L PVA ⁽¹⁾ 100 40 16 PVP ⁽²⁾ 30 16 15 AcBuSt ⁽³⁾ 100 100 62 60 70 65 62 60 63 63 62 AE / MM ⁽⁴⁾ 35 38 40 21 21 PVAc ⁽⁵⁾ 38 23 silica ⁽⁶⁾ 16 13 21 12 22 22 22 glycerin 16 surfactant ⁽⁷⁾ 30 9 9.0 9 13 10 13 17 12 9 9 9 anti-foam ⁽⁸⁾ 12 12 12 26 20 12 17 12 12 12 black N772 8 8 8 total water 1800 250 370 630 1200 1000 310 530 690 630 630 620 ⁽¹⁾ polyvinyl alcohol: Rhodoviol 25/140 (Rhône-Poulenc) (Tg: + 49 ° C ***); ⁽²⁾ polyvinyl pyrrolidone: Luviskol K 90 (BASF) (Tg: about + 175 ° C *); ⁽³⁾ 50% aqueous emulsion of a butyl acrylate / styrene copolymer: Rhodopas GS 125 (Rhône-Poulenc) (Tg: -21 ° C **); ⁽⁴⁾ 40% aqueous emulsion of a copolymer d

ethyl acrylate and methyl methacrylate (Tg: + 34 ° C ***); ⁽⁵⁾ 54% aqueous polyvinyl acetate emulsion (Tg: 28 to 31 ° C *); ⁽⁶⁾ hydrophilic amorphous silica: Aerosil 200 (Degussa); ⁽⁷⁾ non-ionic surfactant: Octyl Phenyl Ethylene Polyoxide (Cinnopal OP9 from Henkel); ⁽⁸⁾ anti-foaming agent: BYK 070 (BYK).
* Reference: Encyclopedia of Chemical Technology, 3rd edition, vol. 23.
** Reference: Rhône-Poulenc measurements.
*** Reference: internal measures.

All the coatings formed with the examples of compositions presented are very good to excellent in the "coloring / efflorescence" test.

Example A relates to an aqueous composition based on polyvinyl alcohol (PVA) added with plasticizer. This polymer has a high glass transition temperature (+ 49 ° C.) and does not give the coating formed a rubbery behavior at the usual temperatures for handling and storing tires. The coating obtained is excellent in resistance to migration and very good for its ease of application, on the other hand, it is unacceptable in all tests where significant deformations are imposed on it, in static and in dynamics, because of its too great rigidity. , despite the presence of the plasticizer. This rigidity causes it to detach from the rubber surface which receives it.

Example B presents the simplest solution based on a butyl acrylate / styrene copolymer. This polymer has a glass transition temperature of -21 ° C, consequently, the coating obtained has a rubbery behavior and is much better than the previous one in all the mechanical resistance tests with high deformations in static and dynamic. However, it is only satisfactory in the handling test, insufficient in the friction test and very insufficient in appearance during the aging test due to a sticky nature which penalizes it by making it sensitive to friction and soiling.

Composition C is a first solution to correct this sticky nature by adding silica. The coating obtained is very good to excellent in all tests.

Another solution is presented with coating D, using polyvinyl acetate. Relative to coating C, D is better in handling and heat resistance but is only acceptable in water resistance due to bleaching.

Examples E and F are based on the same butyl acrylate / styrene copolymer to which is added polyvinyl alcohol (E) or polyvinyl pyrrolidone (F). These two coatings have very similar and very good to excellent behaviors in all tests except water resistance tests, washing and aging / mechanical strength where they are acceptable. This is due to the water solubility of these two polymers.

acrylate d'éthyle et de méthacrylate de méthyle, comme second constituant de la composition aqueuse, correspond à l'exemple G. Le revêtement obtenu est meilleur que les deux précédents dans les tests de résistance à l'eau et au lavage. La résistance mécanique au vieillissement est elle aussi améliorée.The choice of a copolymer d

ethyl acrylate and methyl methacrylate, as the second constituent of the aqueous composition, corresponds to example G. The coating obtained is better than the previous two in the tests for resistance to water and to washing. Mechanical resistance to aging is also improved.

The mechanical properties and the appearance of the coating formed can be further improved by adding silica to the composition of Example G, this is Example H.

invention est l

exemple I. Sa formulation est très proche de l

exemple H avec un taux de silice inférieur, ce qui donne un revêtement avec un aspect un peu plus brillant. Cette formulation ne comporte pas de produit anti-mousse et cela ne dégrade pas les propriétés de dépôt du film. Le revêtement obtenu est transparent, ce qui a l

avantage de ne pas masquer les marquages apposés sur le flanc des pneumatiques au cours de leur fabrication et de leurs tests. Ce revêtement est particulièrement adapté à la protection des flancs blancs qu

il valorise grâce à son aspect légèrement brillant. Il n

a pas à être enlevé lors de la mise en service du véhicule équipé des pneumatiques ainsi revêtus..A preferred example of an aqueous composition according to l

invention is there

example I. Its formulation is very close to

example H with a lower silica content, which gives a coating with a slightly brighter appearance. This formulation does not contain an anti-foaming product and this does not degrade the film's deposition properties. The coating obtained is transparent, which al

advantage of not masking the markings affixed to the sidewall of the tires during their manufacture and their tests. This coating is particularly suitable for protecting the white sides that

it enhances thanks to its slightly shiny appearance. There n

does not have to be removed when the vehicle fitted with the tires thus coated is put into service.

• AcBuSt + AE/MM + PVP : exemple J ;
• AcBuSt + AE/MM + PVA : exemple K ;
• AcBuSt + PVAc + PVP : exemple L.

Examples J, K and L correspond to three other preferred variants according to the invention. The aqueous composition is then based on a mixture of three polymers:

• AcBuSt + AE / MM + PVP: example J;
• AcBuSt + AE / MM + PVA: example K;
• AcBuSt + PVAc + PVP: example L.

The coatings obtained are excellent in all tests. It should be noted that the resistance to scrubbing in the presence of soap is slightly lower, but it may be useful to be able to easily remove the coating in certain cases.

In all cases, the presence of silica improves the appearance of the coating obtained by giving it a slightly matt appearance (examples H, I, J, K and L). Finally, the presence of carbon black in Examples J, K and L improves the resistance to bleaching in the presence of water and to strong deformations.

A final specific test for ozone resistance was carried out on Example J, the so-called "Volkswagen test" test. The purpose of this test is to assess the ozone resistance of a tire sidewall. This is a static test carried out on a tire cut two centimeters wide taken between the bead wire and the crown plies. The cut thus produced is fixed to a tube 20 millimeters in radius by a brass wire. The surface deformation is around 12%. The test pieces thus conditioned are exposed in an ozone oven under the following conditions: Ozone concentration 200 ± 15 pphm (share per hundred million) Relative humidity 60 ± 5% Temperature 25 ± 2 ° C Duration 46 hours

The test is successful when a visual observation does not reveal any crack initiation.

A tire was aged for four months and then half protected by a coating according to the invention. Control and protected control samples were then taken and tested.

The control samples show pronounced cracks. The protected test pieces have no crack initiation on the areas protected by the coating according to the invention.

This test, the most severe of all the tests requested by automobile manufacturers, unambiguously shows the effectiveness of the protective coating according to the invention.

Claims (19)

Aqueous composition intended to form an anti-migration and anti-zone protective coating on the external surface of a tire, comprising an aqueous emulsion of at least: (a) a polymer called component I, said component I being a homopolymer or a copolymer based on at least one monomer chosen from the group of acrylic, methacrylic and vinyl esters, and having a glass transition temperature of less than 0 ° C. ; and (b) a constituent II chosen from the group consisting of a hydrophilic silica and a homopolymer or a copolymer based on at least one monomer chosen from the group of acrylic, methacrylic and vinyl monomers, said homopolymer or copolymer having a transition temperature vitreous above 25 ° C. The composition of claim 1, wherein component I has a glass transition temperature below - 15 ° C. Composition according to Claim 2, in which component I is a copolymer of butyl acrylate and styrene with a content by weight of styrene of the order of 20%. Composition according to one of Claims 1 to 3, in which component II is a hydrophilic silica in the proportion of 5 to 25 parts by weight per 100 parts of dry polymer. Composition according to Claim 4, in which the content by weight of hydrophilic silica is between 10 and 15 parts per 100 parts of dry polymer. Composition according to

one of claims 1 to 3, in which component II is a copolymer or a mixture of homopolymers of ethyl acrylate and methyl methacrylate. Composition according to Claim 6, in which component II has a proportion by weight of ethyl acrylate of the order of 55%. Composition according to

one of claims 1 to 3, in which component II is polyvinyl acetate. Composition according to either of Claims 7 and 8, in which the proportion by weight of said constituent II is between 35 and 55 parts per 100 parts of dry polymer. Composition according to

one of claims 1 to 3, in which component II is polyvinyl alcohol in the proportion of 10 to 50 parts by weight per 100 parts of dry polymer. Composition according to

one of claims 1 to 3, in which component II is poly (N-vinyl-2-pyrrolidone) in the proportion of 10 to 40 parts by weight per 100 parts of dry polymer. Composition according to one of claims 6 to 8, further comprising a constituent III, said constituent III being a vinyl homopolymer or copolymer chosen from the group of polyvinyl alcohols, poly (N-vinyl-2-pyrrolidone) and copolymers vinyl alcohol / N-vinyl-2-pyrrolidone. Composition according to Claim 12, in which the constituent III has a proportion less than or equal to 40 parts by weight per 100 parts of dry polymer. Composition according to Claim 13, having per 100 parts by weight of dry polymer: (a) from 50 to 75 parts of constituent I; (b) from 15 to 28 parts of constituent II; (c) from 7 to 25 parts of constituent III. Aqueous composition according to one of claims 6 to 14, further comprising a hydrophilic silica in the proportion of 5 to 30 parts by weight per 100 parts of dry polymer. Aqueous composition according to one of claims 1 to 15 additionally comprising a carbon black in the proportion of 1 to 10 parts by weight per 100 parts of dry polymer. Method of anti-migration and anti-zone protection of the surface of a tire in which: - A thin layer of an aqueous composition according to one of claims 1 to 16 is applied to said surface; - said layer is allowed to dry until a coating is formed. The method of claim 17 wherein the thickness of said layer deposited on said rubber surface is such that, after drying, the thickness of said coating is between 1 and 30 µm. The method of claim 18 wherein the thickness of said layer deposited on said rubber surface is such that, after drying, the thickness of said coating is between 3 and 15 µm.